When pro-democracy activists took to the streets of Hong Kong for an annual march on the July 1 anniversary of the territory’s handover to China, they kicked off another regular event: disagreement between organisers and police over how many attended.


The march’s organisers estimated that 550,000 people demonstrated in the former British colony, numbers bolstered by anger over a now-shelved bill that would have allowed extraditions to China. Hong Kong police put the number at 190,000. The Hong Kong Public Opinion Research Institute (HKPORI) said 265,000 people took part.


Stationing a team near the end of the route, where there were few detours for marchers, A video to determine how many people passed through a given area in 30 seconds. The measurements were taken at least every 15 minutes.


Those numbers could then be used to create a picture of how many people passed through the counting location on Hennessey Road, in Hong Kong’s Central district.


Over the course of the entire five-hour march, that amounted to 227,000 people.


However, it is impossible to account for some circumstances, such as people leaving the march before it reached Tamar Park or anyone bypassing the march and going directly there.


That means calculations are not an estimate of the total number taking part in the protest.


Hong Kong police said their number was “only a rough figure solely for the purpose of effective manpower deployment”. Protest organisers did not respond to requests for comment.